Dewaxing process



Patented Nov. 4, 1941 2,261,801 DEWAXI NG PROCESS Per K. Frolich, Westfleld, and Jones I. Wesson,

Tow

nley, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application July 29, 1938, Serial No. 221,974

9 Claims.

The present invention relates to the dewaxing of mineral oils and is especially concerned with the removal of waxy constituents from wax-bearing petroleum oils. The invention is more particularly concerned with the use of improved dewaxing aids selected from the class of polymerized or heat thickened fatty oils. The present application is a continuation-in-part of our joint application Serial Number 43,326 filed October 3, 1935, now issued as Patent Number 2,150,370.

It is well known in the art to remove waxy constituents from petroleum oils, particularly lubricating oils, by various means. In these processes the lubricating oil is usually diluted with a suitable diluent and the mixture chilled a sufilcient amount to cause crystallization of the waxy constituents. These waxy constituents are then removed in any suitable manner, as for example, by allowing the mixture to settle and removing the wax by sedimentation. The wax crystals are also removed by means of filtering or by centrifuging the chilled mixture. In these processes in order to facilitate the formation of the wax crystals and in order to secure a more desirable wax crystalline structure, as well as to increase the settling rate, it has been the practice to add various so-called settling or dewaxing aids. These dewaxing aids are effective in securing desirable results in a dewaxing operation. However, particularly desirable and efiective settling or dewaxing aids are relatively diflicult to manufacture and are therefore quite expensive.

We have now discovered a class of improved dewaxing aids which give very desirable and efiective results and which are relatively inexpensive and economical to manufacture. The dewaxing aids of our invention are selected from the class of heat thickened fatty oils or glycerides which are present in animal and vegetable oils. The dewaxing aids of our invention are high molecular weight polymers of fatty oils which are soluble in petroleum oils. The preferred substances are those polymers having a viscosity above 1000 seconds Saybolt at 210 F., preferably having a viscosity above 1500 seconds in the range from 2000 to 3000 seconds at 210 F. Particularly desirable substances are polymerized glycerides which have been prepared by polymerizing oils of the class of non-drying or semi-drying oils. These oils are very desirable in that they may be polymerized to very high viscosities and the resulting polymers are completely soluble in petroleum oils at temperatures at which the waxy oil solvent and dewaxing aid are mixed. These oils also produce a polymer having the property of reducing the pour point of waxy mineral oils when added thereto. These oils further produce a polymerized product which is light in color and is very stable and not subject to further decomposition or thickening. A small amount of acid sometimes develops during the polymerization, especially where a very high vacuum is not obtained, and this may be removed by washing with soda, but preferably by adding to the polymer a small amount of a light hydrocarbon lubricating oil, such as a spindle or neutral oil, then heating and. flashing the same in order to remove the mineral oil by vaporization and at the same time the acid materials are vaporized and removed, but if the vacuum maintained on the system is sufiiciently high the acid can be maintained at so low a figure that the product is practically acid free.

The preferred polymers of the present invention are prepared from various oils of this class, as for example, beech nut oil, brazil nut oil, cameline oil, cottonseed oil, curcas oil, maize oil, mustard oil, ravison oil, sesame oil, soy bean oil, candle nut oil, hempseed oil, nigerseed oil, poppyseed oil, sunflower oil, tung oil, walnut oil and the like. Rapeseed oil polymers and cottonseed oil polymers are particularly effective as a dewaxing aid.

These high molecular weight polymers when used as dewaxing aids give unexpected improved results in a dewaxing process. A higher yield of wax-free oil is obtained in a minimum of time and with a clear separation. It is not entirely understood in what manner the dewaxing aids of the present invention operate insofar as they seem to affect the wax crystallization structure, resulting in a cleaner separation of the wax and resulting in a higher yield of dewaxed oil in a minimum of time. It is, however, believed that the dewaxing aid of the present invention operates by forming a protective colloidal coating over the waxed particles as they are precipitated by cooling and thus lowers the effective volume of the wax and its gel forming tendencies by displacing adsorbed oil. The protective colloidal film does not appear to have the tendency to adsorb any of the oil or solvent layer, but permits better settling and a clearer separation of the waxed particles from the oil.

The dewaxing aids of the present invention may be prepared in any desirable manner. While voltolization may be employed, an especially desirabie and economical product is obtained by simple heat thickening of the preferred glyceride under either vacuum or atmospheric pressure. As previously mentioned, the preferred dewaxing aids are prepared by polymerizing initial materials belonging to the less unsaturated group known as the non-drying and semi-drying oils. These substances generally have iodine numbers within the range from 10 to 200 and preferably from 50 up to about 125. The polymers may be prepared at atmospheric or at super-atmospheric pressure. However, the polymers are preferably prepared by thickening the glycerides at a temperature from 500 to 700 F. while under reduced pressure or vacuum and in the absence of oxygen. A mixture of desirable fatty oils may be used and a portion of hydrocarbon oil may also be added to the material being polymerized in order to aid the polymerization reaction. In general, the amount of hydrocarbon oil added to the polymerization reaction should be in the range from about 10% to 60%. The polymerization reaction is carried out for a time suflicient to secure a product having a viscosity Saybolt of at least 1000 seconds at 210 F., preferably having a viscosity Saybolt of from 2000 to 3000 seeonds at 210 F. By adjusting the factors involved, the time of heating may be varied con siderably, for example, as short as 3 to 5 hours or to 20 hours or more. Ordinarily it is preferred to adjust the factors so as to provide a time of to hours for heating in order to control the polymerization reaction more accurately. Dewaxing aids having a viscosity in the range from 3000 to 7000 seconds at 210 F. may also be readily prepared by the proper choice of glyceride and polymerization conditions without congealing or gelling of the mixture. The dewaxing aid of the present invention may also be prepared by adding a small amount of sulfur to the polymerization reaction to produce polymers containing from about .01 to about .5% sulfur.

In the accompanying drawing there is diagrammatically shown apparatus for carrying out the invention. When using these heat thickened glycerides as dewaxing aids in order to secure an improved dewaxing process, the oil to be dewaxed is first dissolved in a solvent or diluent. Al-

though the dewaxing aids of the present invention give especially desirable results when used with a liquefied hydrocarbon diluent such as propane, other suitable solvents, as for example, naphtha, lower aliphatic alcohols. esters, ketones, chlorinated hydrocarbons, mixtures of hydroaromatic hydrocarbons and the like are satisfactory. The amount of diluent used will vary widely, depending upon the particular diluent being used, as well as upon the type of mineral oil being dewaxed. It is generally preferred to use from 1 to 4 volumes of diluent per volume of oil.

Any suitable amount of dewaxing aid may be employed which will optirnumly affect and modify the wax crystalline structure. In general, it is preferred to add from 0.1 to 3%, generally about 0.5% of the dewaxing aid to the mixture.

The mixture is then chilled in any suitable manner at the optimum rate in order to precipitate the wax crystals. The chilled mixture may be then handled in any suitable manner in order to separate the precipitated waxy constituents from the oil, as for example, by sedimentation, filtering or centrifuging.

In order to further illustrate the present invention, the following example is given which Example 1 A Pennsylvania spindle oil was dewaxed by diluting with 200% of liquefied propane and then chilling at the rate of 1 F. per minute to a temperature of 36 F. The chilled mixture was then filtered in a batch filter.

Another quantity of the same Pennsylvania spindle oil was treated in a similar manner except that 0.5% of a heat thickened rapeseed oil was added. The mixture was chilled at the rate of 1.1 F. per minute to a temperature of -37 F. The chilled mixture was then filtered in the same type filter as in the first operation.

The data on the respective operations were as follows:

Table 1 Dewaxing a Penna. spin lo oil 0.5% of heat f g gg polrgrmerized used 0 used Liquefied propane used --per cent-- 200 200 Ch lling rate per minute F i l. i Chilled to F -36 37 Filtering rate. -volumes per 10 minutes" 1. 52 4. 1 Yield of dewaxed oil --.-per cent 60 82. 1 Pour point of oil"--- 4 0 Melting point of wax. IL- 98 122 From the above data, the marked superiority secured in a dewaxing operation 'by the use of the dewaxing aid is readily apparent. The filtering rate is over two and one-half times greater when using the dewaxing aid of the present invention and the yield of dewaxed oil is approximately 25% larger. The pour points of the dewaxed oils are approximately the same and the melting point of the wax secured when using the dewaxing aid of the present invention is approximately 25% higher.

This invention is not limited by any theories of the mechanism of dewaxing aids nor by any details which have been given merely for purposes of illustration, but is limited only in and by the following claims in which it is intended to claim all novelty inherent in the invention.

We claim:

1. Process of dewaxing oils which comprises diluting the oil with a dewaxing solvent, adding to the solution a small percentage of a polymerized glyceride which is contained in and is the chief constituent of a heat thickened fatty oil and has a viscosity above 1,000 seconds Saybolt at 210 F., said polymerized glyceride being light in color, practically acid free, substantially completely soluble in mineral lubricating oils, and capable of reducing the pour point of waxy mineral oils when added thereto, chilling the solution of wax-containing oil and polymerized glyceride to a wax separation temperature, removing the wax and recovering the dewaxed oil from the remaining solution.

2. Process according to claim 1 in which the quantity of polymerized glyceride added is between 0.1 and 1.0%.

3. Process according to claim 1 in which the said dewaxing solvent is liquefied propane.

4. Process of dewaxing oils which comprises diluting the oil with a dewaxing solvent, adding to the solution a small percentage of a polymerized semi-drying oil having a viscosity above 1,000 seconds Saybolt at 210 F., being light in color, practically acid free, freely soluble in mineral lubricating oils and capable of reducing the pour point of waxy mineral oils when added thereto, and having been prepared by subjecting the semi-drying oil to prolonged heating at a temperature below 700 F. while under reduced pressure, chilling the solution of wax-containing oil and polymerized oil to a wax separation temperature, removing the wax and recovering the dewaxed oil from the remaining solution.

5. Process of dewaxing petroleum lubricating oils which comprises diluting the oil with a dewaxing solvent, adding to the solution a small percentage of a polymer of a semi-drying oil, light in color, miscible with mineral lubricating oil, containing a small amount of sulfur, having a viscosity of at least 1,500 seconds Saybolt at 210 F., and having the property of reducing the pour point of waxy oils when added thereto, chilling the mixture to a wax separation temperature, removing the wax, and recovering the dewaxed oil from the remaining solution.

6. Process of dewaxing petroleum lubricating oils which comprises diluting the oil with a dewaxing solvent, adding to the solution a small percentage of a polymer of rapeseed oil, having a viscosity above 1,000 seconds Saybolt at 210 F., being freely soluble in mineral lubricating oils, and capable of reducing the pour point of waxy mineral oils when added thereto, and prepared by subjecting the rapeseed oil to prolonged heating at a temperature from about 500 F. to 700 F., while in the absence of oxygen, chilling the mixture to a wax separation temperature, removing the wax, and recovering the dewaxed oil from the remaining solution.

7. Process of dewaxing petroleum oils which comprises diluting the oil with a dewaxing solvent, adding to the solution a, small percentage of a polymer of rapeseed oil, said polymer being light in color, substantially free of acidity, containing from .01% to about .5% sulfur, freely soluble in mineral oils, having a viscosity of at least 3,000 seconds Saybolt at 210 F., and hav-: ing the property of reducing the pour point of waxy lubricating oils when added thereto, chilling the mixture to a wax separation temperature, removing the wax and recovering dewaxed oil from the remaining solution.

8. Process of dewaxing petroleum lubricating oils which comprises diluting the oil with a dewaxing solvent, adding to the solution a small percentage of a polymer of rapeseed oil having a viscosity above 1,000 seconds Saybolt at 210 F., said polymer being freely soluble in mineral lubricating oils, capable of reducing the pour point of waxy mineral oils when added thereto and prepared by prolonged heating of the oil at a temperature between 500 and [700 F. while under reduced pressure, chilling the mixture to a wax separation temperature, removing the wax, and :ecovering dewaxed oil from the remaining soluion.

9. Process of dewaxing petroleum lubricating oils which comprises diluting the oil with a dewaxing solvent, adding to the solution a small percentage of a polymerized semi-drying oil, said polymer having a viscosity in excess of 1,000 seconds Saybolt at 210 F., miscible with mineral lubricating oils, having the property of reducing the pour point of waxy mineral oils when added thereto and prepared by subjecting the oil to prolonged heating at a. temperature from about 500 to 700 F. while in the absence of oxygen, chilling the mixture to a wax separation temperature, removing the wax and recovering dewaxed oil from the remaining solu- 

